Phylogeography and Introgressive Hybridization: Chipmunks (Genus Tamias) in the Northern Rocky Mountains

Good, Jeffrey M.; Demboski, John R.; Nagorsen, David W.; Sullivan, Jack

doi:10.1111/j.0014-3820.2003.tb00597.x

Cited by 80 publications

(91 citation statements)

References 93 publications

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“…The spatial pattern of genetic variation across species can help to provide an objective assessment of which process is more likely to have occurred because each should produce a specific spatial pattern [30,72]. The results of our mitochondrial sequences show no strong spatial structure within species.…”

Section: Discussionmentioning

confidence: 97%

“…Both the Bayesian tree and haplotype network indicate the two species are completely intermingled across the landscape. Recent hybridization should show a clustered pattern, where introgressed alleles are more common at or near the contact zone of the two species; in contrast, ancestral polymorphism should be diffuse and uniform across space [30]. However, the spatial patterns described above assume a contact zone between species, and for this study, we were unable to obtain samples of both species from the same location.…”

Section: Discussionmentioning

confidence: 99%

“…It was previously accepted that the morphological differences in bacular morphology in western chipmunks mechanically prevented hybridization between species and was considered a strong pre-mating barrier to gene flow [43,80]. However, several recent studies have documented both historical and ongoing hybridization in two non-sister species of Tamias and suggest that it may be more common in the genus than previously thought [30,31,42]. Our analyses provide little or no evidence for current introgression across the species boundaries; however, the potential for contemporary gene flow between these species where they come into close proximity in the southern portion of their range exists.…”

Section: Discussionmentioning

confidence: 99%

“…Despite well-characterized differences between species, these two taxa share a close genetic legacy, and in order to distinguish between the possibility that this similarity resulted from recent common ancestry versus reticulation subsequent to divergence (e.g., [30,31,42]), we examined the morphology of specimens taken from geographically adjacent versus distant localities to test for morphological intermediacy, using the same geographic groupings in the molecular comparison (Figure 1). We examined three data sets separately.…”

Section: Methodsmentioning

confidence: 99%

“…More specifically, we focus on two questions 1) did T. alpinus diverge from T. minimus in association with late-Pleistocene glacial dynamics and 2) is there evidence for contemporary or historical introgression as reported in other species-pairs of chipmunks [30,31]. To address these questions we examine morphological characters and genetic variation and population structure at one mitochondrial gene and 14 microsatellite loci.…”

Section: Introductionmentioning

confidence: 99%

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Diversification of the Alpine Chipmunk, Tamias alpinus, an alpine endemic of the Sierra Nevada, California

2014

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BackgroundThe glaciation cycles that occurred throughout the Pleistocene in western North America caused frequent shifts in species’ ranges with important implications for models of species divergence. For example, long periods of allopatry during species’ range contractions allowed for the accumulation of differences between separated populations promoting lineage divergence. In contrast, range expansions during interglacial periods may have had homogenizing effects via increased gene flow following secondary contact. These range dynamics are particularly pronounced in the Sierra Nevada, California, given the complex topography and climatic history of the area, thus providing a natural laboratory to examine evolutionary processes that have led to the diversity patterns observed today.ResultsHere we examined the role of late Pleistocene climate fluctuations on the divergence of the Sierra Nevada endemic Alpine Chipmunk (Tamias alpinus) from its sister taxon, western populations of the Least Chipmunk (T. minimus) from the Great Basin. We used one mitochondrial gene (cytochrome b) and 14 microsatellite loci to examine the evolutionary relationship between these species. Mitochondrial sequence data revealed that T. alpinus and T. minimus populations share mitochondrial haplotypes with no overall geneaological separation, and that diversity at this locus is better explained by geography than by species’ boundaries. In contrast, the microsatellite analysis showed that populations of the same species are more similar to each other than they are to members of the other species. Similarly, a morphological analysis of voucher specimens confirmed known differences in morphological characters between species providing no evidence of recent hybridization. Coalescent analysis of the divergence history indicated a late Pleistocene splitting time (~450 ka) and subsequent, though limited, gene flow between the two lineages.ConclusionsOur results suggest that the two species are distinct and there is no contemporary introgression along their geographic boundary. The divergence of T. alpinus during this time period provides additional evidence that Pleistocene glacial cycles played an important role in diversification of species in Sierra Nevada and North America in general.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Diversification of the Alpine Chipmunk, Tamias alpinus, an alpine endemic of the Sierra Nevada, California

2014

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Introgressive hybridization in southern African baboons shapes patterns of mtDNA variation

Keller

Roos

Groeneveld

et al. 2009

American J Phys Anthropol

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Species, as main evolutionary units have long been considered to be morphological entities with limited hybridization potential. The occurrence of taxa which maintain morphological distinctness despite extensive hybridization is an interesting phenomenon. To understand the evolution of these taxa, descriptions of contemporary morphological and genetic variation are essential, also to reconstruct sound phylogenies. Baboons, with their wide geographic range, variant morphotypes, and extensive hybridization offer an intriguing model for those studies. We focus on the complex situation in southern Africa that, in contrast to east Africa, has been neglected in terms of baboon hybridization history. We aim to clarify the distribution and identify possible overlapping zones between different, previously described mitochondrial (mt) DNA clades of baboons that do not match with the ranges of traditionally recognized species. On the basis of the widespread sampling and mitochondrial cytochrome b gene sequencing, we constructed a phylogenetic tree that separates representatives of the two southern African baboon species, yellow and chacma baboons, into six clades: southern, northern and eastern chacmas, Kinda baboons and southern and Luangwa yellow baboons. The ranges of the chacma clades come into close contact or overlap in two regions in the Republic of South Africa and Namibia. Our phylogenetic reconstruction reveals mitochondrial paraphyly for chacma and yellow baboons, which is probably caused by introgressive hybridization and subsequent nuclear swamping, whereby males of the chacma morphotype population from the south invaded the yellow morphotype population in the north bringing their morphotype into a population that maintained its yellow baboon mtDNA.

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Vocal divergence is concordant with genomic evidence for strong reproductive isolation in grasshopper mice (Onychomys)

Campbell

Arévalo

Martin

et al. 2019

Ecology and Evolution

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Behavioral barriers to gene flow often evolve faster than intrinsic incompatibilities and can eliminate the opportunity for hybridization between interfertile species. While acoustic signal divergence is a common driver of premating isolation in birds and insects, its contribution to speciation in mammals is less studied. Here we characterize the incidence of, and potential barriers to, hybridization among three closely related species of grasshopper mice (genus Onychomys). All three species use long‐distance acoustic signals to attract and localize mates; Onychomys arenicola and Onychomys torridus are acoustically similar and morphologically cryptic whereas Onychomys leucogaster is larger and acoustically distinct. We used genotyping‐by‐sequencing (GBS) to test for evidence of introgression in 227 mice from allopatric and sympatric localities in the western United States and northern Mexico. We conducted laboratory mating trials for all species pairs to assess reproductive compatibility, and recorded vocalizations from O. arenicola and O. torridus in sympatry and allopatry to test for evidence of acoustic character displacement. Hybridization was rare in nature and, contrary to prior evidence for O. torridus/O. arenicola hybrids, only involved O. leucogaster and O. arenicola. In contrast, laboratory crosses between O. torridus and O. arenicola produced litters whereas O. leucogaster and O. arenicola crosses did not. Call fundamental frequency in O. torridus and O. arenicola was indistinguishable in allopatry but significantly differentiated in sympatry, a pattern consistent with reproductive character displacement. These results suggest that assortative mating based on a long‐distance signal is an important isolating mechanism between O. torridus and O. arenicola and highlight the importance of behavioral barriers in determining the permeability of species boundaries.

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Phylogeography and Introgressive Hybridization: Chipmunks (Genus Tamias) in the Northern Rocky Mountains

Cited by 80 publications

References 93 publications

Diversification of the Alpine Chipmunk, Tamias alpinus, an alpine endemic of the Sierra Nevada, California

Diversification of the Alpine Chipmunk, Tamias alpinus, an alpine endemic of the Sierra Nevada, California

Introgressive hybridization in southern African baboons shapes patterns of mtDNA variation

Vocal divergence is concordant with genomic evidence for strong reproductive isolation in grasshopper mice (Onychomys)

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